1. Field of the Invention
The present invention relates to a bearing system and balancer.
2. Description of Related Art
Conventional engines for vehicles, such as motorcycle engines, have a balancer for reducing the vibration of the engines housed in the crankcase.
In general, the balancer is used to cancel an inertial force generated by a reciprocating component represented by a piston and a con'rod. The balancer has a balance weight that rotates in the direction opposite to that of the crankshaft at the same speed. The balance weight is disposed coaxially on the shaft of the crankshaft or on a shaft different from the crankshaft. In either case, the balance weight is driven by the power transmitted from the crankshaft.
The balance weight disposed coaxially with the crankshaft has a boss through which the shaft of the crankshaft passes. The boss is supported rotatably around the outer circumference of the shaft via a slide bearing. The slide bearing is press-fitted in a bearing hole opened in the boss. The shaft of the crankshaft is fitted in the slide bearing with clearance therebetween. The slide bearing is supported floatingly by the crankshaft and is rotated with the balance weight.
Referring to Japanese Patent Document JP-UM-B-50-32641, the slide bearing that supports the balance weight rotates in the direction opposite to that of the crankshaft. The reverse rotation doubles the relative velocity generated between the crankshaft and the slide bearing at the maximum, which increases the load on the slide bearing. This poses disadvantages of decreasing the life of the slide bearing and generating extraordinary wear, which may cause seizing, in the slide bearing.